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Saturday, April 30, 2011

G. Svensson & J. Karlsson, J. Climate (2011), On the Arctic wintertime climate in global climate models

On the Arctic wintertime climate in global climate models

Gunilla Svensson*
Department of Meteorology, Stockholm University, Stockholm, Sweden
Johannes Karlsson
Jet Propulsion Laboratory, California Institute of Technology, USA


Energy fluxes important for determining the Arctic surface temperatures during winter in present-day simulations from the CMIP3 Multi-Model dataset are investigated. The model results are evaluated over different surfaces using satellite retrievals and ERA-Interim. The wintertime turbulent heat fluxes vary substantially between models and different surfaces. The monthly median net turbulent heat flux (upward) is in the range 100 to 200 Wm−2 and −15 to 15 Wm−2 over open ocean and sea-ice, respectively. The simulated net longwave radiative flux at the surface is biased high over both surfaces compared to observations, but for different reasons. Over open ocean, most models overestimate the outgoing longwave flux while over sea-ice it is rather the downwelling flux that is underestimated. Based on the downwelling longwave flux over sea-ice, two categories of models are found. One group of models which shows reasonable downwelling longwave fluxes, compared with observations and ERA-Interim, is also associated with relatively high amounts of precipitable water as well as surface skin temperatures. This group also shows more uniform air mass properties over the Arctic region possibly as result of more frequent events of warm-air intrusion from lower latitudes. The second group of models underestimates the downwelling longwave radiation and is associated with relatively low surface skin temperatures as well as low amounts of precipitable water. These models also exhibit larger decrease in the moisture and temperature profiles northward in the Arctic region which might be indicative of too stagnant conditions in these models.
*Corresponding author address: Gunilla Svensson, Department of Meteorology, Stockholm University, SE-106 91 Stockhholm, Sweden., E-mail: 

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